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How CD pregaps gained their hidden track superpowers

235 points| shortformblog | 1 year ago |tedium.co | reply

134 comments

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[+] ssl-3|1 year ago|reply
One less-secretive way I've seen pregaps used is for live recordings.

The crowd noise betwixt songs can be contained in a pregap, so that it is only ever heard when listening to the album straight-through (instead of in shuffle or track-program mode).

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Another fun feature of audio CDs is indexes.

A disc can have 99 tracks, and each track can have some pregap (including track 1, as the article discusses). And each of these 99 tracks can be further subdivided with 99 index markers.

This gives a CD the theoretical ability to have 9,801 selectable audio segments.

Although realistically, I've only owned a couple of CD players that even displayed index numbers and exactly one CD player (a Carver TL-3300) that allowed a person to seek to a given index number within a track.

(And I've only known one CD to actually make use of indexes in any useful manner, which was a sound effects CD from the early 1980s that had a lot more than 99 sounds on it -- all organized by tracks, and sub-organized by index marks. I just can't think of the name right now.)

[+] kevin_thibedeau|1 year ago|reply
My personal CD ripping script is configured to leave all pregaps after track one at the end of the preceding track when splitting them out as individual files. It gets ripped in one DAO pass for guaranteed preservation of all samples when using gapless playback on live recordings. Track navigation then works just like a real CD without having to listen to an incongruous section of audio meant to link the previous track on sequential play or, even worse, missing it altogether.

I have a classical CD from the 80's with index marks for different movements within within the individual compositions represented by a handful of tracks. My understanding is that DG was the only publisher routinely using them. That required some manual intervention to convert the indices to separate tracks. Sony was pretty good about providing index nav. on their full size stereo players. At least until their perpetually cruddy remotes eventually failed.

[+] pseudosavant|1 year ago|reply
I mastered a CD in 2000 for a band that wanted a secret track at the end. I came up with a novel way to do it.

There were a dozen regular tracks. A bunch of empty ones. And the final track over about a dozen tracks of varying length with no gap. Used all 99 tracks.

I could only pull it off with this CD burning software that didn’t have a UI. It took a text file as input at the command line. But it could do everything from almost every color of spec (Red Book, Blue Book, etc) for CDs.

[+] AkBKukU|1 year ago|reply
I'm curious if you have a specific example of an album with the crowd noise between tracks like that? I collect and rip hundreds of CDs and am always on the look out for edge case discs to further hone my tools.

On your pregap + 99 indexes remark, the "pregap" is the space between index 00 and 01 which continues on up to index 99. Players seek to index 01 as the start point of the track. There is no separate pregap designation. I've paid special attention to this because it is a difficult problem to solve as many discs have space between tracks stored in index 00-01 but rarely is there anything audible in there after the first track. The only example I have of this is a specialty music sample disc, Rarefaction's A Poke In The Ear With A Sharp Stick, that has over 500 samples on the disc accessed by track + index positions.

As a sidebar based on the later comments in the thread, I've made it a habit to rip and store every audio CD as BIN/CUE+TOC using cdrdao. This allows me to go back and re-process discs I may have missed something on. But that is imprecise even because it usually breaks bluebook discs with multiple sessions to store data due to absolute LBA addressing. Also the ways different CD/DVD drives handle reading data between index 00-01 on track 1 is maddening. Some will read it, some will error, and the worst is those that output fake blank data.

[+] davidgay|1 year ago|reply
I have an early CD (Bach's Goldberg variations, played by Glenn Gould) which is one track with 31 index markers.

My (early) Philips CD player dealt with it fine, but since then it's been a bit of a problem...

[+] LeoPanthera|1 year ago|reply
Semi-related: "Minidisc" is an album by Gescom (who are really Autechre in disguise) released, as the name suggests, only on Minidisc, containing 88 tracks which are designed to be played on shuffle, because Minidisc, unlike CD or any other physical format, can be shuffled with no audible gap between tracks.

Each track is designed to segue into any other so the album is different every time you play it.

[+] qingcharles|1 year ago|reply
I was responsible for some of the first digital content ingestion for the world's record labels back in the late 90s, which was all based around trucks filled with retail CDs being fed into CD-ROM drives and an army of young folks grinding hundreds of track names into a database. (what happens when a truck full of East Asian CDs turns up? what about all those albums by Aphex Twin and Sigur Ros with untypeable names? https://www.treblezine.com/wp-content/uploads/2014/08/aphex-... )

I love these hidden tracks to death, especially the two hidden pregap tracks on Ash's first album, but they caused me unending pain and suffering.

Not only are they an absolute nightmare to rip, often with more than one song per track (so the WAVs have to be edited), the names of the songs are often totally unknown, even to the record labels. What do you even number the things in the metadata?

Added to that, you nearly always didn't even know they were there, so the negative numbered tracks would fail to get ripped and all the other ones in between or at the end would get ripped in weird ways and confuse all the data folk.

https://www.discogs.com/release/984235-Ash-1977

"Help, computer."

[+] afavour|1 year ago|reply
One memorable album using this was Queens of the Stone Age’s Songs for the Deaf. If you rewound from the start of the first track you got 90 seconds of strange sounding (but tuneful) rumbles and bleeps and bloops.

When I looked it up online I found out it was called “The Real Song for the Deaf”. It was literally a song for deaf people, the idea was that if they turned it up enough they’d be able to hear the vibrations forming a song.

For those interested to listen via a more accessible method: https://www.youtube.com/watch?v=XEU01LrnWng

[+] leonard-slass|1 year ago|reply
I have the hardware and the CD. I did not know you could rewind to negative seconds of the first track. Thank you, you have made my day!
[+] mckn1ght|1 year ago|reply
Same for 311’s Transistor. I remember accidentally doing it and wondering if I’d somehow distorted the fabric of spacetime. Took me a while to figure it out.
[+] MOARDONGZPLZ|1 year ago|reply
I read this whole thing twice and I now know what pregaps are and the history but still have no idea why people would put them on a CD or why they’re useful for hidden tracks.
[+] mikepavone|1 year ago|reply
An audio CD is mostly arranged like a single continuous recording. Tracks are added on top of this via the Q subcode channel that gives information about the current location and the ToC stored in the lead-in area (also using the Q subcode channel). In the ToC, each track will have one more indexes that points at a specific location on the disc by minute, second and "frame" (represents 1/75 of a second, basically a sector).

If a CD is properly following the Red Book standard, index 0 will point to a 2 second pre-gap of silentce and index 1 will point to the actual start of audio of the track (additional indices are allowed, but not common). The purpose of the pregap is to make life easier for less sophisticated players that aren't able to seek to a precise frame on the disc. They just have to be able to hit a 150 frame region. However, just because the standard says the pregap is supposed to be 2 seconds and silent doesn't mean it actually has to be. Players generally don't care and by the time the format was popular, even inexpensive players could seek precisely. This allows you to stick audio data before a track that will be skipped by the player when it's trying to seek to that track. If you stick it before track 01, it will be skipped even when just playing the disc through unless you rewind.

[+] monocasa|1 year ago|reply
Basically cd audio tracks have a base sector and a start specified. That allows sectors representing audio before timestamp 0:00 to be represented the track. The reason for this originally was probably to allow the drive to get synchronized before the track started. Enterprising cd masterers put actual hidden audio data in that area which would allow you on some CD players to rewind past 0:00 and then play the hidden audio at the negative timestamp.
[+] barrkel|1 year ago|reply
The writing is not good; I gave up part way through. It's weirdly elliptic and almost autistic in its focus on details and an almost complete absence of a big picture. It could do with some kind of proper context-setting introduction, at the very least.
[+] dylan604|1 year ago|reply
Oh good, so I'm not the only one that thought the article failed to actually state what the superpower was. Some lame ass patent was granted?
[+] add-sub-mul-div|1 year ago|reply
As the article says its like an easter egg, putting a hidden song before the first track of a CD. If the song wasn't in the pregap it wouldn't be hidden. It's just for fun.

(Sometimes songs can also be hidden in tracks at the end of the CD like 99, but that feels less mysterious.)

[+] dec0dedab0de|1 year ago|reply
I remember my friend accidentally found the negative track on a CD and called me up out of breath like aliens just landed. I think it was one of the early AFI albums.We spent the whole weekend checking for negative tracks on every CD we could find.

The negatives between songs were also pretty cool sometimes, Mediocre Generica by Leftover Crack makes very good use of them. Listening to it over streaming or even mp3s ruins the effect, unless someone captured the entire album as one file.

[+] Lammy|1 year ago|reply
> I think it was one of the early AFI albums

I wouldn't call it an “early” album but I found one of these (untitled 18-second intro) on AFI - DECEMBERUNDERGROUND: https://i.imgur.com/XAsFMSR.png

Some others I've run across in my CD collection include…

— on Jonathan Katz - Caffeinated https://i.imgur.com/4ghQadv.jpeg

— the track "Every Time Is The Last Time" on Bloc Party's Silent Alarm https://i.imgur.com/knhbZhA.png

— a kid606 remix hidden in the first track pregap of The Locust's eponymous https://i.imgur.com/sXVFrQI.jpeg

— the "Theme of Coon" (aka Riki) on the third disc of the SaGa Frontier soundtrack https://i.imgur.com/CqTTqpV.png

> The negatives between songs were also pretty cool sometimes

And one of these, the interlude at the end of “High Roller” on TCM's Vegas which is part of the pregap for “Comin' Back” https://i.imgur.com/G5PSCy3.jpeg

[+] WarOnPrivacy|1 year ago|reply
> Mediocre Generica by Leftover Crack

Those names are a rabbit hole event horizon. Album released 9/11, working title of Shoot The Kids At School was rej by label. Follow up was F WTC. Band lives in C-Squat...

[+] nammi|1 year ago|reply
AFI almost always had a "hidden" track after silence following the last track, I figured following the Misfits' tradition
[+] zdw|1 year ago|reply
I've been using https://github.com/whipper-team/whipper to digitize CD's, and it supports identifying Hidden Track One Audio (HTOA) when it exists and is not blank.

Add in MusicBrainz Picard and Navidrome and you have a really nice solution.

[+] chuckufarley|1 year ago|reply
Whipper user here also. If you've not yet encountered it, as it's not as prevalent in repos as Whipper, Cyanrip is always very much worth a look and has come on in leaps and bounds, with recent updates adding (non compliant) .cue sheet support.
[+] Jedd|1 year ago|reply
This specification anomaly sounds like the polycarbonate equivalent of vinyl's multiple-groove capability. [0]

I'd first heard of this for a Monty Python record (wikipedia notes this is in fact the most famous use case) but checked to see if people went for >2 grooves, and seemingly they did. I expect the casting for the pressing was horrendously expensive, which is why it didn't happen an awful lot.

I suppose both mediums shared the less-well-hidden feature where a long silence separated the penultimate from the ultimate track.

[0] https://en.wikipedia.org/wiki/Multisided_record

[+] caf|1 year ago|reply
When I was very young, my parents had a game called 'wacky races' that was based on a multi-groove vinyl. It was a horse-racing game - I can't recall exactly how the gameplay worked, but the vinyl contained racing calls where the races would start the same way but the outcome would be somewhat random depending on which groove the needle ended up following.
[+] alanfalcon|1 year ago|reply
This is supremely cool, thanks for sharing. I'm probably missing something obvious but why would the casting be any more expensive than any other pressing?
[+] omar_alt|1 year ago|reply
I recall a CD of mine had hidden audio before track one circa 1997, a coffee table jungle breakbeat on a Symphonic Black Metal album:

https://www.discogs.com/release/373044-Arcturus-La-Masquerad...

Also on the topic of trying to push the compact disc to its limits a Grindcore group who had a bonus track where "All efforts were made to exceed typical limitations of 16 bit linear digital technology compression, limiting, and equalization curves have been created to deliver maximum gain structure"

https://www.discogs.com/release/4305023-Exit-13-Ethos-Musick

I had a period of bad luck in my youth where I believed all these new enhanced CD's and shaped CD's were damaging the tracking of the lens on my CD player so I gave Exit-13 a swerve and started to listen to safer music ;)

[+] londons_explore|1 year ago|reply
Things like CD's with their large number of partly-compatible extensions shoehorned in remind me that whenever one is writing a specification, one should make sure that every combination of bits/bytes is either valid with defined behaviour, or invalid.

The one exception is a field for "extensions", which should have some bits for 'compatible' extensions (ie. there will be extra data ignored by readers which don't understand them), and other bits for 'incompatible' extensions (ie. you have put a DVD into a CD player).

[+] Neil44|1 year ago|reply
I had a Rammstein ablum, that if you rewound before track 1 there was a black box audio recording of a plane crash were everyone died. It was pretty macabre. I think the CD cover was like a plane's black box if I remember correctly.
[+] Loughla|1 year ago|reply
Reuse, Reise is the album. It was a Japanese aircraft crash. It was on every album but those released in Japan I'm pretty sure.

It's mostly just scrambled alarms and some Japanese yelling. Without the context it's pretty hard to understand what you're listening to.

[+] kstenerud|1 year ago|reply
One compact disc extension I remember well is CD+G. It was pretty wild plugging an Information Society CD into a CDTV and watching the (admittedly crappy) graphics while you listened to music and samples of Leonard Nimoy and DeForest Kelley...
[+] exabrial|1 year ago|reply
I remember discovering “hidden tracks” on the Beastie Boys intergalactic album with my cousins… we were like what on earth is happening as the CD player display glitched out and played this stuff we hadn’t heard.
[+] fnord77|1 year ago|reply
that whole article went into a lot of detail about the history of pregaps, but never says what was actually put on the pregap
[+] sziring|1 year ago|reply
The domain name is how I felt after trying to read the article.
[+] snvzz|1 year ago|reply
Abusing the standard to put songs in gaps was such a bad idea.

I have no idea how they got a patent for such a thing and, even worse, anyone ever did it on actual commercial discs.

[+] ssl-3|1 year ago|reply
Why? Are easter eggs like this harmful to consumers or something?
[+] indus|1 year ago|reply
In the age of attention deficit infused dopamine—-who has the time for an Easter egg?

Instead, engineers and product managers, slow roll quirkiness on social media.